Watford Water Polo Club Under-14s won the London League title on Sunday.
The side defeated Ealing 3-0, Croydon 2-1 and Beckenham 3-2 to set up a final with Chelmsford.
Watford battled to a 2-1 victory in the final.
The Under-18s defeated Croydon 11-8 in the first leg of their play-off championship.
Sam Carling scored six goals while Paul Botje (2), Cami Baker, Hamish Hudson and James Warman were also on target.
Meanwhile, Watford's first team are fourth heading into the final league rounds this weekend.
Only wins over Sutton & Cheam on Saturday and West London Penguins on Sunday will guarantee promotion.
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